Method and device for utilising the waste heat that has accumulated during the supply of forced draught/compressed air to a printing press

Abstract

The invention relates to a method for supplying forced draught/compressed air and drying air to a printing press, whereby the vacuum pumps or compressors required to supply said forced draught/compressed air are arranged together in a room with a separate air supply. The aim of the invention is to homogenise and if possible even condition air, in particular, process air for the printing press, whilst avoiding additional operating costs. To achieve this, the cooling air for the vacuum pumps or compressors is substantially conducted in a circuit, the heated exhaust air of the vacuum pumps and the heated cooling air of the vacuum pumps and compressors is cooled in a heat exchanger and is used to heat drying air that has been separated for this purpose.

Description

[0001] The invention relates in the first instance to a method of using the waste heat which accumulates when suction air/compressed air is supplied to a printing machine, the subassemblies which produce the suction air and/or compressed air being disposed together in a room with a separate air supply.

[0002] Such air-supply arrangements for printing machines are known. It is also known for these to be disposed in a room with a separate air supply, although a large part of the necessary air is taken in from the surroundings, in particular also from the hall in which the printing machine is set up. It has also already been proposed for the subassemblies to be set up in a separate room outside the hall and to take in the corresponding quality of air from these surroundings.

[0003] The disadvantage in all cases, however, is that the air taken in does not always fulfill the criteria provided for the printing process, in view in particular of the paper used there. It is predominantly also the fluctuation in the air values (temperature, humidity) which is disadvantageous. If air is taken in from the printing-machine hall, this can be countered if all the air in the printing-machine hall is conditioned, i.e. prepared by temperature-conditioning. However, this involves very high outlay. If outside air is taken in, the fluctuations in the air values are usually even more pronounced. It is also possible here, however, since it is only for this taking-in operation but with even higher outlay, for conditioning in the sense of temperature-conditioning to be carried out.

[0004] A possible way is thus sought of achieving a certain homogenization, and as far as possible even conditioning, in particular of the process air for the printing machine, the intention nevertheless being, as far as possible, not to incur any additional costs, in particular any additional operating costs.

[0005] This object is achieved first and foremost by the subject matter of claim 1, this being based on the fact that the heated waste air discharged after passing through the subassemblies and the cooling air is cooled by means of a heat exchanger/refrigerant, the refrigerant is then brought to a considerably higher temperature level, in order to increase the temperature, and, furthermore, air which is required for the dryer is heated up in a second heat exchanger. This method, on the one hand, makes it possible, by virtue of the air which serves for supplying the compressors being cooled, to carry out a certain conditioning, if required, that is to say to cool, if necessary, to below the dew point of this air. On the other hand, however, the heat obtained in this way continues to be used, that is to say costs may be saved elsewhere, this being the case in respect of the drying air which is also necessary in a printing machine.

[0006] It is also pertinent that the cooling air for the subassemblies, i.e. the cooling air of the vacuum pumps and compressors, is conducted substantially in a circuit, the heated cooling air/circulating air conducted in the separate room is cooled in a heat exchanger and used for heating up separate drying air.

[0007] It is also important that the waste air is cooled to the extent where, in the case of undesirably high air humidity, dehumidification is achieved.

[0008] Furthermore, it is preferred for the heat extracted from the cooling air/circulating air to be transformed to a higher temperature level than corresponds to the temperature level of the waste air, in order to heat up the abovementioned drying air.

[0009] This transformation may be suitably carried out by means of a heat pump or a heat-pump process.

[0010] It is also particularly important that the cooling and transformation is carried out by means of a circulating refrigerant. Thus, on the one hand, the complete separation of the two circuits is ensured but, on the other hand, reliable transformation, precisely in the heat-pump process, is made possible.

[0011] For those periods of time in which, although the air for the vacuum pumps and compressors is cooled, no heat is removed on the drying-air side, it is also provided that, as an alternative to heating up the drying air (and the recooling achieved here), the refrigerant is routed via a separate recooler.

[0012] In respect of the drying air, it is necessary, beyond the heating which can be achieved by the abovementioned heat-pump heat exchange, for further heating to be provided. For this purpose, it is further preferred for a reheater to be disposed downstream of the heat exchanger heating up the drying air.

[0013] The invention also relates to an installation for supplying suction air, compressed air and drying air to a printing machine, having a separate room in which subassemblies are disposed.

[0014] In order to achieve a suitable but nevertheless cost-effective air supply, the invention proposes in apparatus terms, analogously to the method described for the invention, that a set-up for circulating-air operation is provided in the separate room, a first heat exchanger, connected into the circulating-air operation, is provided for cooling the circulating air, and a second heat exchanger is provided outside the separate room, for heating up the drying air, the first and the second heat exchangers being connected to one another via a refrigerant/heat-pump circuit.

[0015] Furthermore, as far as the installation is concerned, the invention also proposes the details which can further be gathered from the above description, for example that a branch to a recooling means is connected between the first and second heat exchangers.

[0016] It is also possible for a further heat exchanger to be inserted into the waste-air channel of the drying means.

[0017] It is also possible for the heat pump, at the same time, to use the waste heat of further heat sources, for example the heat sources provided by the ink-unit and damping-solution temperature control and, if appropriate, a varnish-cooling arrangement.

[0018] Furthermore, the invention is explained hereinbelow with reference to the attached drawing, which nevertheless merely illustrates exemplary embodiments. In the drawing:

[0019] FIG. 1 shows a diagram of the installation for supplying a printing machine with drying air and suction/blowing air;

[0020] FIG. 2 shows a diagram which forms an addition, supplement and, in part, alternative to FIG. 1.

[0021] Illustrated and described, in the first instance with reference to FIG. 1, is a separate room 1 in which a plurality of compressors 2 and, if appropriate, vacuum pumps 3 are located for supplying a printing machine 4 with compressed air and a vacuum. The blower 2 is supplied with the necessary air predominantly by circulating-air operation, which is indicated by the arrows 5, 6. The separate housing, rather than being hermetically sealed, also has ambient openings 7, in order to balance the air supply.

[0022] The heated circulating air, which flows in accordance with the arrow 6, is routed through a heat exchanger 8, in which it is cooled by means of a refrigerant.

[0023] In the case of a practical application example, the cooling air leaves the vacuum pumps and compressors, by means of fans, at a temperature of approximately 30° C. and is cooled again to approximately 15° C. in the heat exchanger 8, this being the case for a quantity of air per fan/blower of approximately 2500 m3 per hour, that is to say, for a practical application example with typically approximately four fans provided, in the case of an air flow of 10,000 m3 per hour.

[0024] The heat-transporting medium is conducted in a circuit, where heat is extracted by means of a compressor 9, and is brought to a different temperature level, typically to the extent where a temperature of, for example, 70° C. is achieved. With a small temperature difference, the heat is passed to a heat-transporting medium and fed to a heat exchanger 11, in which the actual heating of the drying air takes place. For example, the drying air passes into the heat exchanger 11 at 20° C. and leaves it at 65° C.

[0025] In contrast to this diagram, it may also be provided that the heat-transporting medium between the heat exchangers 8 and 10, usually a refrigerant, is passed directly to the heat exchanger 11, so that the lines illustrated therebetween in FIG. 1 are thus dispensed with and/or the heat exchanger 11 is replaced by the heat exchanger 10.

[0026] The two heat exchangers 10 and 11, however, are usually indicated or necessary because provided between these heat exchangers is a connection to a recooler 12, in which recooling takes place in the operating phases in which drying air does not have to be heated up. The heat-transporting medium in the second circuit is circulated by means of a pump 13.

[0027] FIG. 1 further illustrates that it is possible to provide a connecting line 27, by means of which air is extracted from the room 1 by way of a suction blower 28 and can be fed into the line 29, through which the drying air flows. This has the advantage that the air, which is possibly dehumidified downstream of the heat exchanger 8, as has also already been explained in detail above, can be used as drying air or, as is usually the case, can be mixed with the drying air. It is thus advantageously possible to reduce the humidity content of the drying air. Furthermore, it is also possible to provide a bypass flap 30 in the line 27, in order, if appropriate, for ambient air to be added or for only ambient air to be taken in.

[0028] In respect of the possible removal of dry air from the room 1 or of air being dried by the heat exchanger 8 in the room 1 as such, it may also be provided, if necessary from the point of view of the operating states, that humidifying subassemblies are provided upstream of the compressors 2, in order for it to be possible for the blowing air to be conditioned, if appropriate, to a more humid setting. If appropriate, this may also be achieved, alternatively or in addition, with a bypass to the ambient air, with the result that some ambient air is taken in directly by way of the compressors, from outside the room 1.

[0029] In the case of the installation diagram of FIG. 2, the heat exchanger 8′ corresponds to the heat exchanger 8 according to FIG. 1 and the heat exchanger 11′ corresponds to the heat exchanger 11 according to FIG. 1.

[0030] Furthermore, in the case of the installation diagram of FIG. 2, a cold compressor 9′ and an intermediate heat exchanger 10′ is also provided in a manner corresponding to FIG. 1. The following modifications and supplements are provided in addition:

[0031] A branch line 14, which leads to a heat exchanger 15, is connected in the return from the cold compressor 9′ to the heat exchanger 8′, the line 13. Air 17 flowing out of a printing-machine dryer 16 is cooled in the heat exchanger 15. The refrigerant heated in this way, in turn, is directed to the cold compressor 9′ and, together with the refrigerant flowing out of the heat exchanger 8′ following heating up, directed, in the line 18, to the cold compressor 9′. The refrigerant is also compressed in the cold compressor 9′ in a manner corresponding to the method in the case of the installation diagram according to FIG. 1, and is thus heated, and fed to the heat exchanger 10′ in the heated state. Here, the heat is transmitted to a heat-carrier medium, in this case a water/glycol mixture, flowing in the circuit formed by the rest of the lines 19, 20, 21 and 22. The heat is fed to the dryer 16. Downstream of the dryer 16, by means of the line 20, the mixture is routed through a condenser 23 and then fed to the heat exchanger 10′ again by means of a pump 24.

[0032] It is also possible for the subassemblies made up of the heat exchanger 8′, cold compressor 9′, heat exchanger 10′ and refrigerant pump 25 to be accommodated in a separate cooling module, indicated by the dashed lines designated 26.

[0033] In particular for heating up the drying air in the heat exchanger 11 or 11′, it is also possible to use further heat sources provided by the printing machine, for example the main drive of the printing machine, the ink-unit temperature control, the waste-air system of the printing machine and the waste air from the dryer system of the printing machine, it being possible for suction extraction to take place here, for example, at individual dryers. It is also possible to use, for example the waste heat from UV stations or infrared stations.

[0034] Insofar as the above is based on heat carriers in the form of refrigerant or a water/glycol mixture, it goes without saying that it is also possible to provide the conventional heat-carrier medium—water. If appropriate, this can then be “transformed upward” via a particular heat pump in order to achieve the desired high temperatures.

[0035] All features disclosed are (in themselves) pertinent to the invention. The disclosure content of the associated/attached priority documents (copy of the prior application) is hereby also included in full in the disclosure of the application, also for the purpose of incorporating features of these documents in claims of the present application.

Claims

1. A method of supplying suction/compressed air and drying air to a printing machine, vacuum pumps and compressors which are necessary for supplying suction air/compressed air being disposed together in a room with a separate air supply, characterized in that the cooling air for the vacuum pumps and compressors is conducted substantially in a circuit, in that the heated waste air of the vacuum pumps and the heated cooling air of the vacuum pumps and compressors is cooled in a heat exchanger and is used for heating up separate drying air.

2. The method as claimed in claim 1 or in particular as claimed therein, characterized in that the waste air is cooled to the extent where, in the case of undesirably high air humidity, dehumidification is achieved.

3. The method as claimed in one or more of the preceding claims or in particular as claimed therein, characterized in that the heat extracted from the waste air is transformed to a higher temperature level, in order to heat up the drying air.

4. The method as claimed in one or more of the preceding claims or in particular as claimed therein, characterized in that the transformation is carried out by means of a heat pump.

5. The method as claimed in one or more of the preceding claims or in particular as claimed therein, characterized in that the cooling and transformation is carried out by means of a circulating refrigerant.

6. The method as claimed in one or more of the preceding claims or in particular as claimed therein, characterized in that, as an alternative to heating up the drying air, the refrigerant is routed via a separate recooler.

7. The method as claimed in one or more of the preceding claims or in particular as claimed therein, characterized in that a reheater is disposed downstream of the heat exchanger heating up the drying air.

8. The method as claimed in one or more of the preceding claims or in particular as claimed therein, characterized in that the drying air at least partially comprises previously dehumidified air obtained, if appropriate, upon implementing the method according to claim 1.

9. The method as claimed in one or more of the preceding claims or in particular as claimed therein, characterized in that use is made of further heat sources in particular from the printing process for heating up the dryer and/or the dryer air.

10. An installation for supplying suction air, compressed air and drying air to a printing machine, having a separate room in which subassemblies such as vacuum pumps and compressors are disposed, characterized by a set-up for circulating-air operation in the separate room, by a first heat exchanger, connected into the circulating-air operation in the separate room, for cooling the circulating air and by a second heat exchanger outside the separate room, for heating up the drying air, the first and the second heat exchangers being connected to one another via a refrigerant/heat-pump circuit.

11. The installation as claimed in claim 10 or in particular as claimed therein, characterized in that a branch to a recooling means is connected between the first and the second heat exchangers.